Multifault testability of delay-testable circuits

This paper investigates the relationship between path-delay-fault testability and multiple stuck-at-fault testability in multilevel combinational circuits. It is shown that a complete robust path-delay-fault test set may not detect all multiple stuck-at faults in multilevel circuits. We also show that path-delay-fault testability does not imply multiple stuck-at-fault testability in multilevel circuits, contradicting a recent paper. Certain path delay tests are also shown to be invalidated by the presence of untestable or untested multiple stuck-at faults.